Continuation of work that defines the nature of rod and cone visual pigment and molecular orientation, kinetics of formation of photoproducts and diffusional mobility in outer segment membranes using advanced microphotometric techniques. Structural change in rod membranes associated with visual excitation. Properties of aging rod membranes. Role of Ca ions and other ions in visual receptor transduction. BIBLIOGRAPHIC REFERENCES: Laties, A.M., Bok, D. and Liebman, P.A. Procion yellow, a marker dye for outer segment disc potency and rod renewal. Exp. Eye Res. 23: 139-148 (1976). Kaplan, M.W. and Liebman, P.A. Slow bleach-induced birefringence changes in rod outer segments. J. Physiol. 265: 657-672 (1977).